aaron burnett, out front starts right now. out front next breaking news, a letter globed to contain a deadly poison has been intercepted at the u.s. capitol. is it another terrorist attack? plus who set off the deadly bombs at the boston marathon. we have new photos to show you. and a mother's grief over the loss of her father. >> good evening, everyone, i'm erin burnett, welcome to our viewers in the youth and around the world. we do begin tonight with breaking news, a u.s. senator

targeted, an envelope that has tested positive for the deadly poison ricin was addressed to senator roger wicker. he's a senator from the state of mississippi. dana bash broke this news first here, she's on the phone from washington. dana what more are you learning about this targeted attack and senator wicker? >> well, first off let me give you. mike brooks is our law enforcement analyst, he is being told that senator wicker now has protective detail, meaning he has security around him, because of the fact that he received this letter which was tested positive for the poison ricin. let me just go back and tell you what we learned, and that is that what happened was this envelope came addressed to senator wicker, it tested once positive for riciricin, they te

it two more times, so three times positive for ricin, so as we speak, this envelope has been sent to a facility in suburban washington, in maryland to get yet another test on ricin. this is something that we learned very quickly, actually as and even before most u.s. senators learned, they were briefed not too long ago earlier this evening from the senator sergeant at arms and they were told that this certainly is essentially very harmful, but they were also calmed a bit by reminding them that this is the reason why they have a facility that's offsite where they sort your mail, it doesn't come directly to their offices. >> it's offsite because of the anthrax that was mailed to members of congress after 9/11. >> exactly. >> do you know more about ricin? it can be incredibly deadly in an incredibly tiny amount.

>> reporter: it can be deadly in a tiny amount. but according to the department of homeland security, their website, they actually categorize this as cat gore b which means it's certainly dangerous but not as dangerous as anthrax, which as you mipgsed was september to a couple of senators back in 2001. they said it's most deadly when it is injected but not as much when it is inhaled or people are exposed another way. and one thing that is interesting to know is that after that anthrax attack 12 years ago now, they completely changed the whole process of how mail comes to the u.s. capitol. it's done off site. they go through and they test things for this exact reason. so senators coming out of this briefing tonight erin said they felt comfortable that this is exactly why the process works the way it does. i remember back then in 2001, i was, many reporters and others who were around who had to take the anti-virus cipro as a

precaution. we're not sure what the people in the mail facility have to do, if they have to take precautions, but we're waiting to see what's going on with them. >> dana is continuing to dig on that part of the story. next i want to go to possibly some new clues on the worst attack since 2001. this is basically a before and after scene of a bomb blast at the boston marathon. let me show you before first. you can see the light colored bag next to a mailbox up against a barricade along the marathon route. look at that for one more second. i'm going to flip it to the second one. we have blurred this a little bit because of the graphic nature of the human beings that are in the picture at that point. but there is no bag there. now, these photos have been turned over to the fbi.

they're looking at the pictures to determine whether that bag could have contained the second bomb. we know the point of detonation was very close to where the bag was located, but i do want to emphasize this, because it's so uncertain, we also know that the fbi said late today that it had determined that both of the explosives for both detonations were placed in dark colored nylon bags or backpacks. obviously what you see there is a light colored one. but with so many question marks and this investigation by admission of the fbi, the boston police, the boston mayor, the governor of massachusetts depletely wide open, any picture matters. drew is in boston now. drew, what do you know? >> i know rick delaurean was asked specifically about the very picture that you just showed your viewers. he said, look, we have got lots of pictures to go over. we can't rule it in, we can't rule it out. but as you said, erin, the one

thing they seem to be confident of, that they released just late this afternoon is that each of these bombs was contained inside a black nylon bag. they were very specific about that. so was there a black nylon back inside the bag that we're seeing on the screen? we just don't know. the fbi says we don't know. but that's what they were most confident of is these black nylon bags. >> drew, just watching, you were there, i was listening to that conference and it seemed to me that the take away was they didn't know. they had that one saudi national that they have been questioning, the person is deemed to be not of interest, not related to this at all, just in the wrong place at the wrong time. but it seems from there, there's nowhere to go. do they know more than what they're saying or do they really not know? >> based on what they said, based on experience covering these things, if they knew more than they are telling us, we would have gotten a lot less information and a lot less quite

frankly, please for the public's help on this. you've got two bombs in two separate locations in a heavily crowded area in a place that was swept for bombs twice before the event took place and they really have nothing, erin, i hate to be so blunt but that is the take away. i want you to listen to what the special agent in charge side to the general public. help us. take a listen to this. >> the person who did this is someone's friend, neighbor, co-worker or relative. we're asking anyone who may have heard someone speak about the marathon, or the date of april 15, in any way, that indicated that he or she may target the event to call us. someone knows who did this. cooperation from the community will play a crucial role in this investigation. we asked that businesses review and preserve video surveillance, video and other business records in their original form.

>> reporter: 24 hours after this event, erin, we don't have a possible description of a suspect, a car a motive, anybody claiming responsibility. it really was stunning to hear and see all those law enforcement officers basically asking for the public's help in trying to solve this. they are working hard, they're trying to piece together the bomb, the fragments, the residue, etc., all taken to quantico, trying to re-enact the bomb, that's kind of standard procedure and also they mentioned the pressure cook never one of the black nylon bags, then a possible pressure cooker was as strong as they could determine that to be. >> drew griffin, thank you very much. certainly amazing, kind of brings back to me, i remember talking to former press secretary leon panetta who said his biggest fear was a lone wolf attack would be the hardest thing to track and that's what

we are looking agent right now. national security analyst and homeland and former security advisor to president bush. what about this issue that we could be looking at a lone wolf, and as drew just said, we don't have a possible description of this person, no one has claimed responsibility. there's no motive. will we find this person? >> the lone wolf is the hardest in any investigation you rely on communication and interaction with others as one of your first leads. i think it's unfair to suggest that this is sort of unusual. they've just gotten through the crime scene exploitation, they have sent that information down to quantico, to the fbi bomb facility. they will get a lot of important leads and information from there. there are thousands of hours of videotape that they have to painstakingly go through.

they're back in 24 to 36 hours out from this massive attack with all these injuries and all these fatalities, and they don't have a suspect. you shouldn't be -- i think we have got to be careful of criticizing law enforcement in sifting through all the information they have. >> do you think it may take a much longer period of time to find out who's responsible? >> i agree completely with fran especially in a situation where no one has taken credit, so in this case where it's completely anonymous, it dutsz does make it very much different. i would like to get back to an earlier story the ricin, i had a source close to the investigation that told me that all tests for ricin did not come back positive. the following two did not, the second fest was negative and the third was inconclusive, so now they're waiting for an additional test at a more

sophistica sophisticated facility in maryland to be more definitive as to whether we actually have ricin. so as of now, they're not completely positive it's ricin. so they're not 100% accurate. more extensive testing is going to have to be done to make a determination of ricin in that envelope. >> as you said, maybe they did not. do you think, though, tom, that they would be looking at a link between this and what happened in boston? the ricin and what happened in boston? because these people are remembering back to 9/11, that after 9/11 that anthrax was sent to washington or do you think it's coincidence? >> they will be looking for it to be a link but as in the anthrax case, it was not related to 9/11, it was completely

different individuals believed responsible. so in this case, if that ricin would be a key factor in if the envelope was mailed, it's not something that was a copy cat or someone just threw this into the mail after the incident yesterday. it's going to determine whether or not it's positive. if it's not positive, we don't have a story and there's no link to be made. >> as we said, we're going to keep you updated on that ricin story, and the more developments we get through the hour, we're going to bring them to you of course. coming up, what we now know about the terrorist attack in boston. now there's remnants of those devices, and what clues those remnants provide. and we're going to take you to the chesterton area of boston where a vigil is being held by family and friends of the 8-year-old child, the little boy who died yesterday. ♪

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new clues tonight about the explosive devices that killed three and injured more than 180 another the boston marathon. the fbi says the bombs were most likely made using pressure cookers filled with metal, nails and perhaps ball bearings. that's what we heard from surgeons that we have spoken to given the injuries they have seen. it's believed the bombs were placed inside dark colored duffel bags with nylon exteriors and placed close to the finish line. joe johns with what we now know about the devices. >> reporter: even before the dust started to settle, authorities were asking what kind of an explosives device created this? the picture of the bombs now

emerging is that they were deadly but crude. a federal law enforcement official with knowledge of the boston bomb investigation tells cnn, the bombs were hidden in bags. >> among items partially recovered are pieces of black nylon which could be from a backpack and what appears to be fragments of bebes and nails thought to be contained a pressure cooker device. >> reporter: it is likely but not certain that a timing device was used to set off the bomb. and doctors say that the bomb was meant to kill or maim as many people as possible. >> due to the number of sharp objects that we found inside people this bomb possibly had metallic fragments in them and we removed pellets and nails. >> reporter: mike buchard is a former top official with the

bureau of alcohol, tobacco and firearms. >> it could be a simple device, but that's all you need, it's an anti-personnel device, and that's all you need. >> reporter: the pressure cooker bomb is not knew, there's plans for it on the internet. the failed terrorist who tried to blow up times square in 2010 tried a variation on the idea but it didn't work and pressure cooker style bombs are a common form of ied use inside both afghanistan and iraq, made famous by this english language article in an al qaeda terrorist magazine known as "inspire." >> this doesn't necessarily mean that is jihadist or al qaeda inspired, but it's striking that there are close parallels between the description of the devices in boston and this

recipe in al qaeda's "inspire" magazine. >> reporter: important to say that authorities have not told us if they have figured out whether the boston bombings were the result of international terrorism or if they believe this was a homegrown attack. erin? >> i want to bring in re lopez now a former member of the fbi hazardous office for 22 years, and ray, get your fake on this. you just heard joe reporting that this pressure cooker type of device has been discussed in the al qaeda magazine and of course are common in ieds in both iraq and afghanistan. does this suggest to you that this could be an attack that had some sort of foreign inspiration or is that not as far as you would go? >> well, erin, hello and i would say basically the pressure cooker is just a vessel. other people have used it in the past and the mere fact that it's on the internet and the other publications to be used as an

ied with pretty detailed instructions on how to create these kind of things, it's kind of out there, anybody can pick this up, either a domestic or foreign person who wants to hurt us. >> there have been at least two instances, reiay of use of pressure cooker devices in the united states. one of three devices in the may 2010 times square bombing and army private first classes th that -- had pressure cookers in his possession according to the fbi. do you think we're going to see more devices of this type? >> over the years, we have had many domestic bombings here in the united states and one of the key features in many of those bombings is that they were pipe bombs, traditional pipe bombs two to three inches in diameter,

with end caps or you could scoot and end cap and put a fuse in there. in order to purchase one of these, people were running the risk of having the hardware store or the store where you purchase these, someone actually calling law enforcement saying, hey, you know, this is very odd. so i think terrorists or criminals have kind of adjusted. and have gone to something that could do equally or more damage, which is you can pick up at almost any store. >> and wouldn't stand out as unusual in any way. i want to show you also, ray, what we showed at the top of our program, the before and after pictures from whdh, it shows a light colored bag as you can see in front of the barrier there that was leaning next to a mailbox, which obviously is extremely bizarre, we're looking here at the route of the marathon and then in the second image, which we have blurred just because of the graphic

nature of it, that bag is gone. our drew griffin said, look, we know the fbi is looking for a dark nylon bag, but it is possible a dark nylon bag was inside the light nylon bag, making this picture perhaps more important to the investigation. i know you've been looking at these pictures and studying them. what do you see? >> well, a couple of things stand out, one as you mentioned earlier was the mailbox. i think that that proximity of that light colored bag, the black bag that contained the ied, i think there would have been significantly more damage, it might have been tipped over, it might have been on its side. it would have been more crushed than you see in the picture. but it could be the synonymous with the black bag being behind or under the feet of where the crowd was at. i'm not sure if there was a stand or space where people were standing that actually blew that bag forward.

it appears to me that i would say given the damage or the lack of damage on the green post office box on the side there, it may have been in another location. >> all right, well, thank you very much, ray lopez, 22 years experience in counter terrorism. we're going the talk to the chair of the house homeland security committee in a moment. we're going to talk about if he knows who's responsible, what -- plus you'll hear from the mother of krystle campbell one of the three people killed in yesterday's bombings. (train horn) vo: wherever our trains go, the economy comes to life.

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breaking news, a moment of silence was held before the opening of the baseball game in cleveland. >> a moment of silence for the victims of yesterday's tragedy in boston. we all stand as one with the people of boston in a time of grief and pain and express our support for their healing and recovery in the days ahead. please join us now in a moment of silence. thank you all very much. >> still to come, what we are learning about the explosive devices used during the attack. the chairman of the house

homeland security committee mike mccall has been briefed and he's going to come here on cnn live next to tell us what he knows. plus we go to boston's dorchester neighborhood where a candle light vigil honoring the youngest victim of the attack. [ coughs ] [ angry gibberish ] i took something for my sinuses, but i still have this cough. [ male announcer ] a lot of sinus products don't treat cough. they don't? [ male announcer ] nope, but alka seltzer plus severe sinus does it treats your worst sinus symptoms, plus that annoying cough. [ breathes deeply ] ♪ oh, what a relief it is [ angry gibberish ] [ breathes deeply ] ♪ oh, what a relief it is

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devices that killed three people and injured at least 183 mored a yesterday's bottom marathon. mcmccall told reporters today that it was most likely gunpowder that was used in the devices and chairman mccall joins me now. i want to start with the other breaking news we had tonight is reports of a letter containing ricin sent to the republican senator from mississippi. i'm wondering what your understanding is of that at this moment and what your understanding is of any possible link to what happened in boston. >> it did test positive for ricin, we have no evidence whatsoever connecting the two, between the ricin incident and the boston bombing incident. since 9/11, since the anthrax scare, we have an offside mail

ma silty, and it actually worked in this case, caught in an advanced screen from getting to capitol hill in the offices. ricin is very targeted, almost a assassin like lethal dose. the terrorists are more interested in killing, in having mass casualties so it would be inconsistent with the terrorist philosop philosophy. >> what's your understanding tuesday why, senator wicker, do you have any information on that at this time, and we hear that he has been assigned a security detail in light of this. is that the case? >> i think a security detail would be appropriate in light of the events. i think a lot of members of congress have threats and this one is certainly one to be taken seriously. i don't have any background, i know roger well, he's a nice guy, i don't know why anybody would want to do this to him. >> what can you tell us now about the device? i know earlier today you said

there was gunpowder perhaps inside this pressure cooker, as we understand from law enforcement officials. what else do you know right now about the devices themselves that were used at the boston marath marathon? >> i think the important piece of evidence is that they are pressure cookers. why is that important? the 2010 times square bomber had a variation of it. remember the ieds are the vehicle of choice to be used by the terrorists. they have been used extensively in afghanistan and pakistan. so what's happening right now is the explosive materials found at the scene have been sent to quantico for a forensics examination. this will be very telling in terms of clues, hopefully leading us to the terrorists. all sorts of fingerprint information with respect to the backpowder, the ball wearings, the device itself and actual fingerprints that could be on these materials as well. so it's almost like a book of

information will come out of this forensics examination and it should come out hopefully for the next 24 hours. and i think that's going to greatly enhance the investigation in the joint terrorism task force to apprehend these terrorists and bring them to justice. >> and that timeline is a crucial metric. i remember when defense secretary leon panetta said that his greatest fear for the united states is a lone wolf attack because it would be impossible to pick up before hand and perhaps then impossible to identify it afterwards. and many have said this could be that kind of situation. are you concerned because there's no suspect? last night they said they had someone they were questioning. that person now is not a perso of interest. what can you tell us about who they're looking at right now and your fears of perhaps never finding the person. >> of course it's a huge concern. usually within the first four hours, that's your best opportunity to apprehend the

criminal, in this case the terrorist. i do think the video they have from the scene will help facilitate the appearance of the individual who dropped this backpack into the trash cans. and i think the explosive forensics that's going to be done i think will give us a lot of information to move this information forward. but like you, i am concerned and the lone wolf homegrown terrorist is probably the most difficult to prevent and most difficult to apprehend after the fact. because they're operating virtually alone and not within a circle or network of a terrorism organization. >> and chairman a time question, we talked about this last night and it still remains at the epicenter of the investigation and that is was it a foreign, someone from outside the united states or was it a american who was the perpetrator of this attack? obviously we have reported that pressure cookers were used in al qaeda inspired acts and of course also you can see how you

can use them in the al qaeda magazine. but they have also been common in other sorts of attacks, does that lead you down a path of foreign or domestic? have you had any indications as to which it will be? >> i think the jury's still out, whether it's a foreign or terrorist related attack. one possibility that's not mentioned is that it could be foreign inspired, like the inspired magazine that al qaeda put out that shows you how to make these bombs in your mother's kitchen essentially. the ideaa it could be inspired like the general hassan out there, the homegrown terrorist, i would could be inspired by the foreign organization and pulled off by a homegrown inside the united states. we really don't know. the jury is still out. we really won't know until this forensics comes back from the examination of the bombing device and until the perpetrators are actually and prehebded. >> chairman mccall, good to talk

to you again sir. a boston family is reeling after learning that one of their loved ones died in the bombings. krystle campbell was 26 years old and she was described as generous and vivacious, initially her parents were told that she had survived but it was a case of mistaken identity. you heard from her mother who just came out to talk to reporters, it was heart breaking to watch that. >> reporter: it was terrible, she was so overcome by grief, erin she could barely speak, and you can imagine the roller coaster of emotion this is family has been through. let me just explain what happened with krystle campbell. she went to the marathon with her friend, they showed up, they got caught in the first explosion and initially doctors at massachusetts general hospital told the campbell family that krystle had survived, that krystle campbell had survived that they were working on her to save her leg.

her parents waited patiently. they were finally let into the room and they looked down and discovered it was not in fact their daughter, it was their daughter's friend and at that point, they waited to find out what had in fact had happened to krystle campbell. about an hour after that, erin, a detective came in and showed them a picture and it was at that point they discovered their daughter had not survived. a little earlier today, her mother came out, she tried to speak to reporters, it was very difficult for her. i just want you to listen to how she tried to speak about her daughter. >> we are heart broken at the death of our daughter krystle, he was a wonderful person. everybody that new her loved her. she loved her dogs, she used to -- she was always smiling, you couldn't ask for a better daughter. i can't believe this has

happened. she was such a hard worker in everything she did. this just doesn't make any sense. >> thank you. >> what kind of daughter was she, ma'am? >> she was the best, you couldn't ask for a better daughter. >> the grief of that family, jason, just horrible to see. what is massachusetts general saying about this and how this confusion happened? >> reporter: well, we have called them several times, erin, at one point i did get a spokesperson on the phone and basically what she said is they are learning about this just as much as the media is. in fact they said they learned about this alleged mistake this afternoon. they said they were still trying to get information about exactly how this all could have happened. they said they are in the process of trying to put together a statement. we are still waiting for that statement, but as you can imagine, this whole terrible, terrible mixup has just compounded the grief for this family. >> yes.

just horrible, thank you very much, jason. there's a candle light vigil happening right now in the dorchester area of boston where family members are gathering to acknowledge the youngest victims of yesterday's bombings, an 8-year-old, martin richard, he was killed near the finish line, she was watching the marathon with his family. his mother and sister were also injured by the blast. gary, that story just every time you see that little boy's face, it's horrible. >> reporter: yeah, it really is. it's very hard when you're dealing with tragedy like the oklahoma city bombing in 1995, where certainly children were killed, you remember that forever. that happened 189 years ago and i think of that every time i cover a tragedy. this candle light vigil you're talking got erin, this is really impressive. it just started out. you can see all the candles in

the background. this was word of mouth, this six hours ago that didn't exist, there's perhaps 1,200 people in this park in dorchester remembering the three people who perished in this tragedy just about 30 hours ago. and we are only a few blocks away from the home of martin richard, a little 8-year-old boy who skied. what's so sad, is that as we speak, his sister is lot in the hospital. his younger sister is a dancer and she lost one of her legs in the blast and another one of her legs might have to be amputated. also his mother's in the hospital. his other brother's okay, the father's okay, but one can only imagine what it's like right now erin for this father and this brother who are not only dealing with the loss of their son, their 8-year-old son who was such a nice boy, but also worrying so much about his wife and his little daughter still in the hospital. >> the unfairness and the horror of this, you talk about a sister, a dancer, who lost her

leg and as you said, fighting for her second leg tonight. i know that his mother also suffered a brain injury, right? it's an unbelievable tragedy for so many in one family. >> reporter: right, it is. and this father is a very brave man, he actually came up with a written statement he gave us. i want to read it to you because it's so poignant and important. he talked about his child. he said my dear son martin has died from injuries sustained in the attack on boston. my wife and daughter are both recovering from serious injuries, we thank our family and friends and those we have never met for their thought and prayers. i ask them to pray for our family as we grieve martin and we also ask for privacy as we grieve privately. all the other people here in boston who are suffering so much after this horrifying and horrible day yesterday.

>> and we're going to talk about what forensic experts are looking for in those videos and photographs. you know that today, law enforcement officials say if you were there, if you have any picture, they need it. what are they looking for in these pictures? we're going to tell you exactly and show you after this. i turned 65 last week.

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who planted the bombs at the boston marathon and when did they do it? that was the crucial question that authorities are trying to answer tonight. they don't have a suspect yet and they don't have a motive. boston police commissioner ed davis says two bomb sweeps were done prior to the explosions and didn't dedetective anything unusual. what are investigators zeroing in on if you had to say the time and the space? >> they're really focusing on three hours right around the end of the course. let me bring in the course and talk about what we mean right now. there was a final security sweep done along the coast one hour before the elite runners finished. they went along the course and they cleared it here one hour before the top runner came in,

then two hours after that, that's when this started happening. there was the first blast near the finish line and then we had the second blast 12 seconds later. let me turn the map around so you can look right down the racecourse here. one of the things they're looking at is this side of the racecourse, this path down the middle here is very hard to cross in a big, big race like this. so in all likelihood, wherever the bomber or bombers came from, it was likely on this side of the path and they weren't able to cross. that's why both bombs were on the same side. so bar they looking for anybody who saw anything, and really saw something that matters. for example this picture is exacting a lot of attention. because of that picture, that's near the site of one of the blasts. the question would be from investigators did anybody photograph anybody carrying that package or another package that fits the description that they're at here. that's what they want. there is a difference between a

witness, and somebody who just heard something. they want to hear from everyone, but the real grail here, is someone who can say on this street and that specifically could be connected. erin? >> tom, let me ask you about something else that's unique about this kind of an event. a marathon, in the modern era, everybody who is running wears a tracker. . that wirelessly transmits exactly every millisecond where they are on the actual marathon route. is that important? >> yeah, it is important, in fact. you wear a timing chip of some sort. every time you pass over the tracking mats, it will tell the race organizers where you are. it's just for running the race. why does that matter? will these runners coming in here being tracked electronically be able to say they saw something? probably not. but you know what they can tell investigators, they can tell investigators where their family and friends were. so if investigators say we have a witness down here who saw a

guy with a black bag and we have a witness down here who saw a guy with a black bag, this is almost unheard of tool. they can then go through the runner data base and say to the runners, were you family and friends in between here? how can we reach out to them and ask them if they saw it? normally in a big event, all the witnesses have been dispersed and the police at their mercy whether or not they come back in. in this case, they know how to reach out and get to them. that could be a huge benefit to this process, erin. >> thank you very much. and as tom talking about every second and every single, you know, snapshot of every moment matters here, investigators at the highest level of the u.s. government are going through mounds of evidence. they're looking at hundreds of thousands of photos, hours and hours of video, trying to find that one incident that might make a break in this case. with massive crowds gathered near the finish line on monday, there's a strong possibility someone photographed someone or something before the deadly explosions. but with so much media in a sense it makes it harder.

is it looking for a needle in a hay stack. the forensic scientist from john jay college of criminal justice. thank you for taking the time. i wanted to show you a few of the pictures we now know law enforcement are looking at carefully and just get your view on these. first, the before and after snapshot from whgh basically showing, as you can see, before there's a nylon light colored bag next to a mailbox and then after it's gone, the picture we have blurred there because of the graphic human nature of the content. when you look at that picture, what do you see? >> well, i think we already know the seat of the explosion. it becomes very important to try to focus in on the exact spot and how the bomb was delivered, how is it disguised? how is it dropped? where was it dropped? and then ultimately to find who dropped it. but looking at these kinds of photos help us focus our

attention on that particular area near that mailbox. that's a critical area. >> right. because i'm saying as a layperson, why is there a mailbox there? i mean, right? fair question. >> u.s. postal service probably put it there. i don't know. >> right. >> but clearly it's important in this particular situation. >> let me take a look at this bag from another angle, another shot we have. you can take a look. this is from earlier in the race. the men's first place finisher is just -- this is a different angle. a policeman it looks like back there to our eyes blocking the actual mailbox. but a forensic expert if you had a lot more time, magnify glasses, all the things you would do, would you be able to determine if it's suspicious? >> it's hard to answer that, but there are methods available to forensic scientists to do enhancement of photographs. >> how do they do that? >> and try to take out iges

and leave in important images, contrast enhancement devices, high resolution. it can be done to a certain extent. >> let me ask you about another shot. this is a shot of the crowd near the finish line and what i wanted to ask you about in this, people will be able to see. faces are recognizable in this. can investigators use biometrics? a way to identify individuals. here the faces are clearly visible, but in many shots they may not be to the average eye. would you be able to identify anybody? >> well, the technology has certainly been developed to do facial recognition. looking at certain points on the face and then comparing it to a data base. we use that at airports. so that is feasible. but this is only a tiny piece of the puzzle with all kinds of surveillance videos in that area. this is a large crime scene. and clearly we're focused on two very, very specific areas. so those videos become extremely important. >> all right. well, thank you very much for taking the time. giving all our viewers a little

bit of a sense of what's going on right now going through picture by picture. and i do want to give you the latest breaking news we have. the chinese consulate has confirmed to cnn that a chinese national is the third person killed in the boston marathon blast. at this point, no name has formally been released. we could tell you now that we know the identity of the third person killed in the bombing terror attack yesterday was a chinese national. we're going to be right back. ♪ (train horn) vo: wherever our trains go, the economy comes to life. norfolk southern. one line, infinite possibilities. governor of getting it done. you know how to dance...

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and as we leave you tonight, we want to remind you about those who died yesterday. to remember who they are. take a look at 8-year-old martin richard of the dorchester neighborhood of boston. that little boy's picture and his face will be emblazoned in all of our minds. a very sweet boy. his mother and sister were two of the people critically wounded in the attack. and there was 29-year-old crystal campbell. a restaurant manager. you heard her mother earlier really unable to even speak. she was so broken by grief in losing her daughter. caring, loving, daddy's little girl. you look at her and realize that person was alive going into a normal day expecting nothing but celebration. and then this happened. and now there's a third victim, boston university graduate student, the one from china, we don't know her